Mechanism of Macroscopic Motion of Oleate Helical Assemblies: Cooperative Deprotonation of Carboxyl Groups Triggered by Photoisomerization of Azobenzene Derivatives

Macroscopic and spatially ordered motions of self‐assemblies composed of oleic acid and a small amount of an azobenzene derivative, induced by azobenzene photoisomerization, was previously reported. However, the mechanism of the generation of submillimeter‐scale motions by the nanosized structural transition of azobenzene was not clarified. Herein, an underlying mechanism of the motions is proposed in which deprotonation of carboxyl groups in cooperation with azobenzene photoisomerization causes a morphological transition of the self‐assembly, which in turn results in macroscopic forceful dynamics. The photoinduced deprotonation was investigated by potentiometric pH titration and FTIR spectroscopy. The concept of hierarchical molecular interaction generating macroscale function is expected to promote the next stage of supramolecular chemistry.     

Reaction of germabenzenylpotassium with TBDMSCl: Unusual trimerization of germabenzene skeletons

Abstract

The reaction of 2-t-Bu-germabenzenylpotassium with Me₂(t-Bu)SiCl (TBDMSCl) resulted in the coupling among two TBDMS-substituted germabenzenes and the germabenzenylpotassium. The structure of the product was determined by X-ray crystallographic analysis. Its formation mechanism was proposed with the help of theoretical calculations.     

Optimizing Charge Switching in Membrane Lytic Peptides for Endosomal Release of Biomacromolecules

Endocytic pathways are practical routes for the intracellular delivery of biomacromolecules. Along with this, effective strategies for endosomal cargo release into the cytosol are desired to achieve successful delivery. Focusing on compositional differences between the cell and endosomal membranes and the pH decrease within endosomes, we designed the lipid-sensitive and pH-responsive endosome-lytic peptide HAad. This peptide contains aminoadipic acid (Aad) residues, which serve as a safety catch for preferential permeabilization of endosomal membranes over cell membranes, and His-to-Ala substitutions enhance the endosomolytic activity. The ability of HAad to destabilize endosomal membranes was supported by model studies using large unilamellar vesicles (LUVs) and by increased intracellular delivery of biomacromolecules (including antibodies) into live cells. Cerebral ventricle injection of Cre recombinase with HAad led to Cre/loxP recombination in a mouse model, thus demonstrating potential applicability of HAad in vivo.     

An estimated quantitative lateral flow immunoassay for determination of artesunate using monoclonal antibody

There have been reports of fake artesunate (ART), which has led to deaths from untreated malaria in South East Asia. To rapidly screen for fake and adulterated ART products in the drug market, a lateral flow immunoassay (LFIA) based on a colloidal gold–monoclonal antibody probe for detection of ART within samples was developed. With this method, the calibration curve for ART was determined by the intensity ratio of the test and control bands at various ART concentrations. The linearity range was 12.5–200 μg/ml of ART. Samples were tested by the developed LFIA and can be calculated for ART contents. The levels of ART in the samples were also confirmed by enzyme-linked immunosorbent assay. The results of the two methods were in good conformance. The proposed LFIA was demonstrated to be a simple and rapid analytical method for detecting ART in the pharmaceutical formulation.     

Synthesis of (Z)-β-(Carbonylamino)alkenylindium through Regioselective anti-Carboindation of Ynamides and Its Transformation to Multisubstituted Enamides

The regioselective anti-carboindation of ynamides by using InBr₃ and silylated nucleophiles was developed to synthesize (Z)-β-(carbonylamino)alkenylindiums. The X-ray crystallographic analysis of an alkenylindium suggested that the reaction proceeded in an anti-addition fashion. In contrast to reported syn-carbometalations of ynamides by using organometallics, a cooperation of InBr₃ and silylated nucleophiles to ynamides achieved an anti-addition, which was supported by DFT calculations. The scope of substrates included various ynamides and silylated nucleophiles, such as silyl ketene acetals and silyl ketene imines. The transformation of synthesized alkenylindiums by iodination, radical coupling, and Pd-catalyzed cross-coupling successfully afforded trisubstituted enamines with high regio- and stereoselectivities.     

The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single‐Crystalline Ordered Mesoporous Nb‐TiO2 and Plate‐like Nb‐TiO2 with Ordered Mesoscale Dimples

Highly ordered mesoporous niobium‐doped TiO₂ with a single‐crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb‐doped TiO₂. The XPS measurements of Nb‐doped TiO₂ showed the presence of Nb⁵⁺ and correspondingly Ti³⁺. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate‐like TiO₂ with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.     

Excellent Stability of a Lithium‐Ion‐Conducting Solid Electrolyte upon Reversible Li+/H+ Exchange in Aqueous Solutions

Batteries with an aqueous catholyte and a Li metal anode have attracted interest owing to their exceptional energy density and high charge/discharge rate. The long‐term operation of such batteries requires that the solid electrolyte separator between the anode and aqueous solutions must be compatible with Li and stable over a wide pH range. Unfortunately, no such compound has yet been reported. In this study, an excellent stability in neutral and strongly basic solutions was observed when using the cubic Li₇La₃Zr₂O₁₂ garnet as a Li‐stable solid electrolyte. The material underwent a Li⁺/H⁺ exchange in aqueous solutions. Nevertheless, its structure remained unchanged even under a high exchange rate of 63.6 %. When treated with a 2 M LiOH solution, the Li⁺/H⁺ exchange was reversed without any structural change. These observations suggest that cubic Li₇La₃Zr₂O₁₂ is a promising candidate for the separator in aqueous lithium batteries.     

Computational study on the interactions of mustard gas with cucurbituril macrocycles

The study on the absorption of toxic gases such as mustard gas by organic host is essential to the development of inexpensive detection and decontamination equipments. Using quantum chemical methods, we propose cucurbituril as an effective host to capture mustard gas. It was found that stable complexes are formed with the inclusion of the toxic gas molecules inside the cucurbituril cavity, compared with the lateral and exterior interactions. Oxygen mustard has a comparable binding energy with sulfur mustard and hence can be used during experimental investigation. Additionally, during the inclusion complex formation, the presence of heteroatoms helps the guest molecules to undergo a larger structural reorganization to get accommodated inside the cucurbituril macromolecule. Atoms‐in‐molecules analysis shows the existence of strong intermolecular CH…O bonding between the guest molecules and cucurbituril macromolecule. The presence of an intramolecular CH…Cl type of bonding accounts for the higher stabilization of sulfur mustard inside the cucurbituril macromolecule. © 2015 Wiley Periodicals, Inc.     

2‐Oxazoline Formation for Selective Chemical Labeling of 5‐Hydroxylysine

Hydroxylation of lysine, one of posttranslational modifications of proteins, generates 5‐hydroxylysine (Koh) and plays a crucial role in regulating protein functions in cellular activity. We have developed a chemical labeling method of Koh. The 1,2‐aminoalcohol moiety of Koh in synthetic peptide sequences was trapped by an alkyne‐containing benzimidate to form a 2‐oxazoline ring. An additional ammonia treatment process removed the undesirable amidine residue formed between benzimidate and lysine. During the ammonia treatment, the oxazoline residue formed at Koh mainly remained intact, and the ring opening to the amide form was observed for only part of oxazoline, indicating that the chemical labeling is amino acid selective. Azide‐substituted biotin or fluorescent dye was attached to the peptide through Huisgen cycloaddition at Koh and converted into an alkyne‐labeled oxazoline form. The Koh‐labeling assay could provide a platform to enhance proteomic research of lysine hydroxylation.